1. Field of the Invention
This disclosure relates generally to analog-to-digital converters, and in particular, but not exclusively, to those used in the readout circuitry of a complementary metal-oxide-semiconductor (CMOS) image sensor.
2. Background Information
Image sensors are ubiquitous. They are widely used in digital still cameras, digital video cameras, cellular phones, security cameras, medical devices, automobiles, and other applications.
Many image sensor applications benefit from an increased high dynamic range (HDR). However, increasing the dynamic range in a conventional image sensor typically means a slower, more complex and increased power consuming analog-to-digital converter (ADC).
One known type of ADC is a floating point ADC. A floating point ADC attempts to increase the overall dynamic range of the ADC by directly performing floating point analog-to-digital conversion. In one example, a floating point ADC includes a programmable gain amplifier (PGA) that amplifies the analog input signal with a gain corresponding to a selected range. However, conventional floating point ADCs may suffer from step/quantization error that will limit the effectiveness of the ADC.